The present invention relates to a method for sizing a cellulosic fiber-containing yarn with a sizing agent consisting of a synthetic copolymer in a non-aqueous medium. More particularly, the present invention relates to a method for sizing a cellulosic fiber-containing spun yarn with an non-aqueous solution of an acrylic or methacrylic copolymer in a halogenated hydrocarbon solvent, in order to prepare a sized yarn having excellent desizing, weaving and processing properties.
It is known that in order to smoothly carry out a weaving process for a spun yarn, it is important that the warp spun yarn is appropriately sized with a sizing agent. In this case, it is required that the sized warp yarn be pertinent to the effect the weaving process with a high efficiency and with no or very few number of yarn breakages and that the sized yarn fabric can be easily completely desized in a simple process. Further, it is required that the sized yarn fabric has excellent processing property, for example, scouring, bleaching and dyeing properties. The term "processing property" used herein, refers to a property of the sized yarn fabric such that the sized yarn fabric can be easily processed into a processed fabric, for example, scoured, bleached or dyed fabric, having a uniform quality.
In conventional sizing methods, the cellulosic fiber-containing yarn is sized with an aqueous solution of a water-soluble sizing agent such as starch, polyvinyl alcohol, water-soluble salts of polyacrylc acid, water-soluble salts of partially esterified polyacrylic acid, and mixtures of two or more of the above-mentioned sizing agents. If the cellulosic fiber-containing yarn is sized by the conventional method stated above, it is difficult to completely desize the sized yarn. Even if the sized yarn is completely desized, the desizing process is complicated or expensive, or requires a large amount of water. Recently, it has become an increasingly important requirement that the desizing process be effected in a simple process without polution and using no or a small amount of water. In order to meet with this requirement, a sizing process for cellulose fiber-containing yarn with a synthetic sizing agent in a non-aqueous solvent, has been developed. The synthetic sizing agent can be removed from the yarn by treating the sized yarn in a non-aqueous organic solvent.
However, it is difficult for the conventional synthetic sizing agents to satisfy all of the following requirements:
1. high adhesive property of the sizing agent for the fibers in the yarn to be sized; PA1 2. no or very few formations of fluff on the sized yarn fabric during weaving; PA1 3. easy shedding of warp yarns in the weaving process; PA1 4. high lubricity of the sized yarn; PA1 5. no or very small separation of the sizing agent from the yarn during the weaving process; PA1 6. no difficulty in supply of the yarn from a reed in a loom; PA1 7. appropriate softness of the sized yarn; PA1 8. proper hardness of the film of the sizing agent formed on the sized yarn; PA1 9. high efficiency in the weaving process; PA1 10. no formation of defects for example, warp streak, warp falling, uneven gloss, on the sized yarn fabric; PA1 11. high desizing property, and; PA1 12. simple operation in the desizing process. PA1 1. When a yarn sized with a polyvinyl acetate or polyvinyl chloride is used as a warp for weaving a fabric, a large amount of sizing agent polymer is separated from the yarn, the separated sizing agent polymer falls down onto a reed of the loom and obstructs the movement of the reed, many warps are broken and many fluffs are formed on the woven fabric. Accordingly, this type of sized yarn cannot be used for weaving for a long period of time. The above-stated disadvantages may be because the sized warp yarn is quickly abraded at a high velocity when the reed moves up and down. PA1 2. The copolymers containing a copolymerized organic acid component are superior in adhesive property for the cellulosic fibers and obstructive property for the formation of fluffs on the woven fabric. However, since such kinds of copolymers and cellulosic fibers are sensitive to humidity, the cellulosic fiber-containing yarns sized by the organic acid-containing copolymer have large variations in tensile strength and elongation with the change of humidity and temperature during the weaving operation. This results in frequent breakages of the warp. PA1 3. Only copolymers having both the glass transition point and Young's modulus within a special range have a good weaving property. PA1 4. The halogenated hydrocarbon and petroleum solvents are proper as the solvent for sizing agent copolymers for the cellulosic fiber-containing yarns. Especially, the halogenated hydrocarbon can provide a sizing agent solution having a high desizing property. PA1 providing a non-aqueous sizing solution by dissolving a sizing agent copolymer in a halogenated hydrocarbon solvent, said copolymer consisting of 20 to 80% by weight of at least one copolymerized monomer component selected from the group consisting of methyl methacrylate, styrene and acrylonitrile and 80 to 20% by weight of at least one copolymerized monomer component selected from the group consisting of acrylic esters of aliphatic alcohols having 1 to 8 carbon atoms and methacrylic esters of aliphatic alcohols having 4 to 8 carbon atoms, and having a glass transition point of 40.degree. to 80.degree.C and a Young's modulus of 1 .times. 10.sup.3 to 1 .times. 10.sup.4 kg/cm.sup.2 ; PA1 impregnating a cellulosic fiber-containing yarn with a desired amount of said non-aqueous sizing solution, and PA1 removing said halogenated hydrocarbon solvent from said impregnated cellulosic fiber-containing yarn.
For example, the Japanese Patent Application Publication No. 12559/1972 discloses a process for sizing, in a non-aqueous solvent, with a synthetic sizing agent consisting of a four-component copolymer containing, for example, acrylic acid and vinyl acetate. The Japanese Patent Application Publication No. 27089/1973 discloses a process for sizing, in a non-aqueous medium consisting of a halogenated hydrocarbon, with a three-component copolymer containing acrylic acid or methacrylic acid and two kinds of esters. The sizing agent copolymers mentioned above are pertinent for sizing the synthetic fiber yarns due to their high adhesive property for the synthetic fiber yarns. Further, the sizing agent copolymers containing a copolymerized organic acid component such as acrylic acid and methacrylic acid, can be easily desized by treating the sized yarn fabric with an alkali aqueous solution. That is, during the treatment, the organic acid component of the copolymer is converted into a water-soluble organic acid salt component, and as a result of the conversion, the copolymer is solubilized in water. The solubilized copolymer is easily removed from the fabric by washing with cold or hot water. However, it has been discovered by the inventors that the copolymers having such organic acid component are not suitable for sizing the cellulose fiber-containing yarns. This is because the organic acid-containing copolymers have a relatively high hygroscopic property and a relatively high affinity to the cellulosic fiber.
Since cellulosic fiber has a high hygroscopic property, if the cellulose fiber yarn is sized by the organic acid-containing copolymer, the resulting sized yarn has a high hygroscopic property. Such hygroscopic yarn varies in its tensile strength and elongation depending upon the variation of temperature and humidity. This variation results in large number of yarn breakages during the weaving process.
Further, the organic acid copolymer is difficult to desize from the cellulosic fiber yarn due to its high affinity to the cellulosic fiber. Even if it seems that the copolymer is almost completely desized from the cellulosic fiber yarn by an organic solvent, a very small amount of the copolymer retained in the cellulosic fiber yarn results in non-uniformity in quality of the scoured, bleached or dyed fabric. If the copolymer is removed from the cellulosic fiber yarn by using the alkali aqueous solution, it results in consumption of a large amount of water. In order to solve the above-mentioned difficulty in the sizing process for the cellulosic fiber-containing yarn with a synthetic sizing agent in a non-aqueous medium and desizing process for the synthetic sizing agent, the inventors have thoroughly studied the preparation and property of the conventional synthetic sizing agents and new sizing agents, utilization of desizing solvents, and kinetic property of the sizing agents during the weaving process for the cellulosic fiber-containing yarns, and the influence of the sizing agent retained in the cellulosic fiber-containing yarn fabrics on the processing property, for example, scouring, bleaching and dyeing properties. As a result of the study, the inventors have discovered the following facts:
Further, due to the high affinity of the organic acid-containing copolymers to the cellulosic fibers, it is very difficult to completely desize the copolymers from the sized cellulosic fiber-containing yarn fabric. A small amount residue of the copolymer in the fabric causes remarkable unevenness in the scouring, bleaching and dyeing property of the sized yarn fabric. Still further, the application of the copolymer results in an increase in the hardness of the sized yarn and formation of uneven gloss on the woven fabric. If a large amount of the copolymer is applied to the yarn, it is necessary to mix an amount of a lubricating agent into the copolymer in order to avoid the above-mentioned disadvantages.